Constant-temperature device



J. SLEPIAN.

CONSTANT TEMPERATURE DEVlCE. APPLlCATlON HL ED JULY 10. 1918.

1,367,102. Patented Feb. 1,1921.

INVENTOR WITNESSESz' Joaeph J/zpiazz.

' XI'TORNEY UNITED STATES PATENT OFFICE.

JOSEPH SLEPIAN, F WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC 8a MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA;

CONSTANT-TEMI'ERATURE DEVICE.

Specification of Letters Patent.

Patented Feb. 1, 1921.

Application filed July 10, 1918. Serial No. 244,333.

To all whom it may concern.

Be it known that I, JOSEPH SLEPIAN, a

' citizen of the United States, and a resident of Wilkinsburg, in'thecounty of Allegheny and State of Pennsylvania, have invented a new anduseful Improvement in Constant.

.Temperatu-re Devices, of which the followin is.a specification.

y invention relates to constant-temperature devices and particularly tomethods of,

and means for maintaining the temperature of, one junction of athermo-couple constant. One object of my inventlon is to provide meanswhereby the junction of a thermocouple may be subjected to a saltmixture that has a definite melting point to thereby maintain thethermo-couple at a constant temperature, irrespective'of the change 1nheating of the mixture or the ambient temperature "to which-it issubjected.

A further object of my inventlon is to provide a device of theabove-indicated character that shall be simple and inexpensive toconstruct and effective in its operation. I

In practising my invention, I provide 'a salt mixture that becomesconductive at a definite temperature. The junction of a thermo-couple,or other devicejthat is to be maintained at a constant. temperature, isdisposed adjacent the surface of the mixture and the mixture is heatedby an alternating current. Since the mixture has a definite meltingpoint and is of such substances that its composition remains un changed,irrespective of the melting caused by heating of the same, thethermo-couple will be maintained at a constant temperature in a film ofthe melted mixture. The mixture may be, for example, a hydrated salthaving an indifferent point in itssolubility curve such as zinc sulfate(7H O). This is a solid below 50 C. but becomes a saturated solution at50 C. Above this temperature it becomes a Water solution of zincsulfate. Therefore, if, at 50 C. heat is removed from the solution, thezinc salt precipitates out but it crystallizes with 7 molecules of waterto produce the solid salt to have the same composition as the solution.Thus, since the remaining solution retains the same'composition,irrespective of the heat applied thereto, the temperature remains at 50until the whole mixture has been converted into a solid zinc tion 23% byweight.

sulfate, with 7 molecules of water of crystallization.

The single figure of the accompanying drawing 1s a diagrammatic view ofa constant-temperature device embodying my inventlon.

A source of alternating current 1 is operatively connected, through atransformer 2, to a circuit 3'comprising a resistor 4 and a conductor 5.A salt mixture 6 is disposed around the conductor 5 and one junction .7of a thermo-couple is disposed adjacent the inner surface of the mixture6 and the conductor 5. A The mixture 6 is composed of a salt having adefinite melting point, at which temperature it becomes a conductor.Thus, when the current traversing the conductor 5 so heats the mixture 6as to cause the same to melt in a film around the conductor 5, thecurrent will fiow through two parallel paths, one through the conductor5 and the other through the melted film of the mixture. The junction 7of the thermo-couple w ll be disposed inthe melted film of the mlxtureand, if the mixture is of the roper materials, the junction will be maitained at a constant temperature, irrespective of changes in currenttraversing the conductor 5. That is, since the composition of themixture does not change, irrespective of the precipitation caused by theapplication of heat, the temperature will be maintained at in which thelatter salt occurs in propor- Above 171.5 (1, this such asbismuth-chlorid and ferric-chlorid mixture is a fluid and, on cooling,both the bismuth-chlorid and the ferric-chlorid precipitate out butalways remains in the proportion of 23% ferric-chlorid. Thus, since thecomposition of the remaining mixture does not change when heat iswithdrawn, the mixture will remain at 171.5 C. until the whole mass hasbecome solid.

Another class of substances suitable for this purpose is a solution ofhydrated salt having an indiiferent point-in its temperature solubilitycurve. An example of this class, of substance is a solution of zincsulfate which is saturated at 50 C. Above 50 (1., it is a water solutionof zinc sulfate. If heat is removed from such a substance at 50 (3., thezinc salt precipitates out but crystallizes with 7 molecules of wa. terto cause the solid salt to have the, same composition as the originalsolution; Thus, as .the salt precipitates out, the remaining solutionhas the same composition, and, therefore, since the melting point of asalt having such a composition is always 50 C., the temperature of thedevice, such as the junction 7 of the thermo-couple, is maintainedconstant until the whole solution has been converted into a solid zincsulfate, with 7 molecules of water of crystallization.

Another material that may be used for the mixture 6 is a eutecticmixture of a solid crystallizing with two different lproportions ofwater in a water solution. 11 example of such a mixture is a solution offerricchlorid in water havin the proportion of 17 gram molecules oferric-chlorid to 100 gram molecules of water. Such a'mixture -1s.a truesolution above 35 0., and, when heat is removed therefrom at 35 0., asolid precipitate forms which is a mixture of ferric-chlorid (7H O) andferric chlorid (5H O) in such proportions as to produce the same totalcomposition as the original solution. Thus, when part of such a solutionsolidifies, the remaining composition is unchanged and the temperatureof the same will remain at 35 C. until the whole is converted into asolid mixture of two hydrated iron salts.

The essential featureof my invention is that the device, the temperatureof which is to be maintained constant, is subjected to a salt that, whenheated, does not change its composition but which melts at a definitetemperature to become a conductor, and thus, lrrespective of the amountof melting caused by the heating, its composition is al ways the sameand is maintained at a defin1 te temperature. That is, the temperaturew1ll remain at the melting point of the salt, Irrespective of a changein .the heating current, or the ambient temperature to which it 1ssubjected.

y 111VeI1t1011 is not limited .to the specific ,salt solutionsdescribed, as various substances may be employed without departing fromthe spirit and scope of my invention, as set forth in the appendedclaims.

I claim as my invention:

1. A constant temperaturedevice comprisin heating means, and a substancethat is a apted to become conducting at a definite temperature and havea constant composition, the means to "be maintained at aconstant-temperature being disposed adjacent the heating means and thesubstance.

ent point 'in its temperature-solubility curve disposed adjacent theheating member to maintain constant the temperature of a thermo-coupledisposed adjacent the surface of the said mixture.

4:. A constant-temperature device comprising a conductor, electric meansfor'heating the conductor, a body of hydrated salt having an indifferentpoint in-its temperature solubility curve surrounding the conductor andadapted to become a conductor at a definite temperature to maintain atthat temperature a thermo-couple disposed adjacent the surface of theconductor.

5. The method of maintaining a device at a constant temperature whichconsists in heating a zinc sulfate (71-1 0) mixture and placing thedevice adjacent the surface of the mixture.

6. The method of maintaining a constant temperature which consists inheating a body of hydrated salt having an indifferent point in itstemperature solubility curve with an electric current. 1

7. The method of maintaining a' device at a constant temperature whichconsists in electrically heating a conductor and a body disposedtherearound that is adapted to melt and become a conductor at apredetermined temperature and disposing the device in a fihn of the bodyat the surface thereof.-

8. A constant-temperature device comprising a hydrated salt mixturehaving an indifferent point in its temperature-solubility curve, andmeans for heating the same,

sald mixture being such that, when heat is crystallizes with water thatthe solid salt has the same composition as the original mixture.

9. A constant-temperature device comprising a hydrated salt mixturehaving an indifferent point in its temperature-solubility curve, andmeans for heating the same, said mixture being such that, when heat isremoved, the salt precipitates out and so crystallizes with water thatthe solid salt has the same composition as the original mixture tomaintain the temperature thereof constant, irrespective of the heatapplied thereto.

-10. The method of maintaining a device at a constant temperature whichconsists in heating -a body, that is adapted to melt and become aconductor having the same composition as the original body, anddisposing the device in a film of the melted body.

11. The method of maintaining a device 5 at a constant temperature,irrespective of thevheat applied thereto, which consists in disposingthe device in a salt mixture that melts at a predetermined temperatureand maintains a constant composition.

10 12. The method of malntaining a constant point in its which consistsin heating a rated salt having an indifferent temperature-solubilitycurve to the temperature of that point and then supplying heat energy tocompensate for the radiation losses.

In testimony whereof, I have hereunto subscribed b 1918.

y name this 22nd day of June,

JOSEPH SLEPIAN.

